We need to be sure that you have the correct Codec installed for your Video.
First step is to find out what codec we need.
1. Download and Run the
GSpot program (
more information). Add your video to it. It will show you what codec is required. In the following example we need a
DX50 codec (see the Red Rectangle, DX50 equals to the DivX codec)

Another free software that tells you about the Codec
MediaInfo:

What is the Codec of your Video?
2. Find and Install the required Codec.
See the download page of AndreaMosaic where you find the link and the instructions to install some Codecs contained in the K-Lite Codec Pack. Please follow carefully those instructions. The "K-Lite: Version 5.6.1 Full" contains several VfW Codecs: XVid, DivX, etc:

If this doesn't help then we have two solutions:
A) Find somewhere else the correct Codec for your video.
or
B) Use a program to convert your Video into one of the K-Lite supported codecs. For example the free
AviDemux.
Note: WMV files are right now not supported. You must convert them into an AVI file (for example), see the post below.
byee
Andrea